Positive resist compositions and patterning process

ABSTRACT

A polymer which is obtained from a combination of (meth)acrylate having a bridged ring lactone group and (meth)acrylate having an acid leaving group with a hexafluoroalcohol group is used as a base resin to formulate a positive resist composition which when exposed to high-energy radiation and developed, exhibits a high sensitivity, a high resolution, and a minimal line edge roughness due to controlled swell during development. The composition also has excellent dry etching resistance.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2004-115088 filed in Japan on Apr. 9, 2004,the entire contents of which are hereby incorporated by reference.

This invention relates to positive resist compositions, typically of thechemical amplification type, adapted for exposure to high-energyradiation, which have a significantly high contrast of alkalidissolution rate before and after the exposure, a high sensitivity, ahigh resolution, a minimal line edge roughness, and good etchingresistance, and which are especially suited as micropatterning materialsfor the manufacture of VLSI or the formation of photomask patterns; anda patterning process using the same.

BACKGROUND OF THE INVENTION

In the drive for higher integration and operating speeds in LSI devices,the pattern rule is made drastically finer. The rapid advance towardfiner pattern rules is grounded on the development of a projection lenswith an increased NA, a resist material with improved performance, andexposure light of a shorter wavelength. In particular, the change-overfrom i-line (365 nm) to shorter wavelength KrF excimer laser (248 nm)brought about a significant innovation, enabling mass-scale productionof 0.18 micron rule devices. To the demand for a resist material with ahigher resolution and sensitivity, acid-catalyzed chemical amplificationpositive working resist materials are effective as disclosed in U.S.Pat. No. 4,491,628 and U.S. Pat. No. 5,310,619 (JP-B 2-27660 and JP-A63-27829). They now become predominant resist materials especiallyadapted for deep UV lithography.

Resist materials adapted for KrF excimer lasers enjoyed early use on the0.3 micron process, passed through the 0.25 micron rule, and currentlyentered the mass production phase on the 0.18 micron rule. Engineershave started investigation on the 0.15 micron rule, with the trendtoward a finer pattern rule being accelerated. A wavelength change-overfrom KrF to shorter wavelength ArF excimer laser (193 nm) is expected toenable miniaturization of the design rule to 0.13 μm or less. Sinceconventionally used novolac resins and polyvinylphenol resins have verystrong absorption in proximity to 193 nm, they are difficult to use asthe base resin for resists. To ensure transparency and dry etchingresistance, some engineers investigated acrylic and alicyclic (typicallycycloolefin) resins as disclosed in JP-A 9-73173, JP-A 10-10739, JP-A9-230595 and WO 97/33198.

Among others, a focus is drawn on (meth)acrylic resin base resistsfeaturing a high resolution. One of the (meth)acrylic resins proposedthus far is a combination of (meth)acrylic units having methyladamantaneester as acid labile group units with (meth)acrylic units having lactonering ester as adhesive group units as disclosed in JP-A 9-90637.Norbornyl lactone is also proposed as an adhesive group having enhancedetching resistance as disclosed in JP-A 2000-26446, JP-A 2000-159758 andJP-A 2002-371114.

Of the outstanding tasks associated with the ArF lithography, it isdesired to minimize line edge roughness and to reduce residues followingdevelopment. One of the factors causing line edge roughness is swellingduring development. While the polyhydroxystyrene used as the resist forKrF lithography, in which the phenol moiety is a weak acidic group andhas an appropriate alkali solubility, is resistant to swelling, polymerscontaining hydrophobic cycloaliphatic groups, which must be dissolvedusing carboxylic acids having a high acidity, are likely to swell duringdevelopment.

The development performance of resists can be quantified by the quartzcrystal microbalance (QCM) technique. The quantity of swell duringdevelopment is reported in Proc. SPIE Vol. 3999, p2 (2000). Although theswelling of a film being developed could not be observed by the priorart film thickness measurement relying on optical interference, the QCMtechnique designed to electrically measure any change of film weightenables to observe any weight increase of swollen film. The citedreference discusses the swelling of ArF resists based on cycloolefinpolymers. Substantial swells are observed when carboxylic acid is usedas the adhesive group.

It was also reported that hexafluorocarbinol groups are effective forreducing the swell. Norbornene having hexafluorocarbinol groupsexperiences minimal swell. Resists based on polynorbornene having suchgroups as the adhesive group are reported in Proc. SPIE Vol. 5039, p70(2003) and Proc. SPIE Vol. 5039, p61 (2003). Acrylates havinghexafluorocarbinol groups are also described in JP-A 2003-40480.

SUMMARY OF THE INVENTION

An object of the invention is to provide a positive resist compositionwhich when exposed to high-energy radiation and developed, exhibits ahigh sensitivity, a high resolution, and a minimal line edge roughnessdue to controlled swell during development, and leaves minimal residuesfollowing development. Another object of the invention is to provide aprocess for forming a pattern using the same.

The inventors continued research works targeting a positive resistcomposition which when exposed to high-energy radiation and developed,exhibits a high sensitivity, a high resolution, and a minimal line edgeroughness due to controlled swell during development, and leaves minimalresidues following development.

For the F₂ lithography, resists using hexafluoroalcohol have beenstudied. It is reported in J. Photopolym. Sci. Technol., Vol. 16, No. 4,p523 (2003) that hexafluoroalcohol has an acidity approximate to that ofphenol and is least swollen in a developer liquid. Also known arepolynorbornene having hexafluoroalcohol and α-trifluoromethyl acrylatehaving hexafluoroalcohol pendants. It has been reported how thesepolymers perform when exposed to ArF excimer laser light. The inventorshave discovered that although a polymer having only hexafluoroalcohol asthe adhesive group is not fully adhesive, a corresponding copolymerhaving copolymerized therein recurring units having lactone as theadhesive group is endowed with a good balance of hydrophilicity,alkaline solubility and adhesion. In particular, when a polymer which isobtained from a combination of (meth)acrylate having a bridged ringlactone group and (meth)acrylate having an acid-labile leaving groupwith an adhesive group having alkaline solubility as typified byhexafluoroalcohol is used as the base resin, there is provided apositive resist composition which when exposed to high-energy radiationand developed, exhibits a high sensitivity, a high resolution, and aminimal line edge roughness due to controlled swell during development,and leaves minimal residues following development. The composition alsohas excellent dry etching resistance.

According to the invention, there is provided a resist compositioncomprising a polymer comprising recurring units of the general formulae(1a), (2a), and (1b).

Herein R¹ is each independently hydrogen or methyl, R² is eachindependently hydrogen, an acyl group of 1 to 10 carbon atoms, or anacid labile group, R³ is hydrogen, methyl or —CO₂R⁸, R⁴ is hydrogen,methyl or —CH₂CO₂R⁸, R⁵ to R⁷ are each independently hydrogen, methyl or—CO₂R⁹, R⁸ is each independently hydrogen or a straight, branched orcyclic alkyl group of 1 to 15 carbon atoms, R⁹ is hydrogen or astraight, branched or cyclic alkyl group of 1 to 10 carbon atoms, X is—CH₂—, —O— or —S—, saving —CH₂— when all of R⁵ to R⁷ are hydrogen. Thesubscripts a1, a2 and b1 are numbers satisfying0≦a1/(a1+a2+b1)≦0.9,0≦a2/(a1+a2+b1)≦0.9,0<(a1+a2)/(a1+a2+b1)≦0.9, and0<b1/(a1+a2+b1)≦0.8.

When exposed to high-energy radiation and developed, the positive resistcomposition comprising the above polymer as a base resin has asignificantly high contrast of alkali dissolution rate before and afterthe exposure, a high sensitivity, a high resolution, and a minimal lineedge roughness due to controlled swell during development, leavesminimal residues following etching, and exhibits good etchingresistance. Owing to these advantages, the composition is fullyacceptable in industrial practice and especially suited as amicropatterning material for the manufacture of VLSI or the formation ofphotomask patterns.

The composition is preferably formulated as a chemically amplifiedpositive resist composition comprising (A) the above polymer as a baseresin, (B) an organic solvent, and (C) a photoacid generator. With thisformulation, in the exposed area, the rate of dissolution of the polymerin a developer liquid is accelerated by acid-catalyzed reaction. Thenthe chemically amplified positive resist composition has so high asensitivity that it is very suitable as the micropatterning materialwhich is currently needed for the manufacture of VLSI. The positiveresist composition may further include a dissolution inhibitor. Theinclusion of a dissolution inhibitor enhances the difference indissolution rate between the exposed and unexposed areas, leading to afurther improvement in resolution. The positive resist composition mayfurther include a basic compound and/or a surfactant. The addition of abasic compound holds down the rate of diffusion of acid within theresist film, leading to a further improvement in resolution. Theaddition of a surfactant improves or controls the applicability of theresist composition.

A pattern may be formed on a semiconductor substrate or mask substrateusing the resist composition of the invention, typically by applying theresist composition onto a substrate to form a coating, heat treating thecoating, exposing it to high-energy radiation, and developing it with adeveloper liquid. Heat treatment may also be carried out after theexposure and before the development. The process may, of course, befollowed by various steps such as etching, resist removal and cleaningsteps. The high-energy radiation typically has a wavelength in the rangeof 180 to 200 nm. The resist composition containing the inventivepolymer as the base resin is especially effective for exposure tohigh-energy radiation in the wavelength range of 180 to 200 nm becauseits sensitivity to the exposure wavelength in the range is very high.

According to the invention, the polymer having copolymerized specificrecurring units having a hexafluorocarbinol group, (meth)acrylate unitshaving a bridged ring lactone group, and (meth)acrylate units having anacid labile group is compounded as a base resin into a resistcomposition, which has a high sensitivity and a high resolution. Thecomposition is minimized in line edge roughness and leaves minimalresidues following development due to controlled swell duringdevelopment, as demonstrated through measurement by the QCM technique.There are thus provided positive resist compositions, especially achemically amplified positive resist compositions, which are suited asmicropatterning materials for the manufacture of VLSI or the formationof photomask patterns.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the thickness versus developing time of aresist film formed from the resist composition of Example 1, as analyzedby the QCM technique.

FIG. 2 is a graph showing the thickness versus developing time of aresist film formed from the resist composition of Comparative Example 1,as analyzed by the QCM technique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Polymer

The resist composition of the invention comprises a polymer or highmolecular weight compound comprising recurring units of the generalformulae (1a), (2a), and (1b).

In the formulae, R¹ is each independently hydrogen or methyl, R² is eachindependently hydrogen, an acyl group of 1 to 10 carbon atoms, or anacid labile group, R³ is hydrogen, methyl or —CO₂R⁸, R⁴ is hydrogen,methyl or —CH₂CO₂R⁸, and R⁵ to R⁷ are each independently hydrogen,methyl or —CO₂R⁹. R⁸ is each independently hydrogen or a straight,branched or cyclic alkyl group of 1 to 15 carbon atoms, R⁹ is hydrogenor a straight, branched or cyclic alkyl group of 1 to 10 carbon atoms. Xis —CH₂—, —O— or —S—, saving —CH₂— when all of R⁵ to R⁷ are hydrogen.The subscripts a1, a2 and b1, representative of the molar proportions ofthe respective units in the polymer, are numbers satisfying0≦a1/(a1+a2+b1)≦0.9,0≦a2/(a1+a2+b1)≦0.9,0<(a1+a2)/(a1+a2+b1)≦0.9, and0<b1/(a1+a2+b1)≦0.8.

Suitable acyl groups represented by R² include acetyl and pivaloylgroups, with those groups having 1 to 6 carbon atoms being preferred.The acid labile group is described later. Suitable alkyl groupsrepresented by R⁸ include methyl, ethyl, propyl, isopropyl, butyl,isobutyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, octyl anddecyl, with those groups having 1 to 12 carbon atoms being preferred.Suitable alkyl groups represented by R⁹ are the same as exemplified forR⁸, with those groups having 1 to 12 carbon atoms being preferred.

Examples of the monomers from which the recurring units of formulae (1a)and (2a) are derived are given below.

In the monomer prior to polymerization, the group attached to the carbonatom of —C(CF₃)₂— is an acetyl group, which is converted to a hydroxylgroup through alkaline hydrolysis after polymerization. In some cases,the hydrogen atom of the hydroxyl group may be replaced by an acidlabile group.

The polymer of the invention should have copolymerized therein recurringunits having hexafluorocarbinol as represented by formulae (1a) and (2a)and recurring units of an ester monomer having a specific lactone ringas represented by formula (1b).

Examples of the monomers from which the recurring units of formula (1b)are derived are given below.

In order that the resist composition be positive working, the preferredpolymer in the resist composition has further copolymerized therein amonomer having an acid labile group represented by the general formula(1c).

Herein, R¹ and R² are as defined above, and R⁷ is an acid labile group.

The acid labile groups represented by R³ and R⁷ in formulae (1a) and(1c) may be identical or different and selected from a variety of suchgroups, preferably from groups of formulae (AL10) and (AL11), a tertiaryalkyl group of 4 to 40 carbon atoms represented by formula (AL12), andan oxoalkyl group of 4 to 20 carbon atoms.

In formulae (AL10) and (AL11), R⁰⁰¹ and R⁰⁰⁴ each are a straight,branched or cyclic alkyl group of 1 to 20 carbon atoms which may containa heteroatom such as oxygen, sulfur, nitrogen or fluorine. The subscript“a” is an integer of 0 to 10. R⁰⁰² and R⁰⁰³ each are hydrogen or astraight, branched or cyclic alkyl group of 1 to 20 carbon atoms whichmay contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine.Alternatively, a pair of R⁰⁰² and R⁰⁰³, R⁰⁰² and R⁰⁰⁴, or R⁰⁰³ and R⁰⁰⁴,taken together, may form a ring with the carbon atom to which they areattached, the ring having 3 to 10 carbon atoms, especially 3 to 8 carbonatoms. In formula (AL12), R⁰⁰⁵, R⁰⁰⁶ and R⁰⁰⁷ each are a straight,branched or cyclic alkyl group of 1 to 20 carbon atoms. Alternatively, apair of R⁰⁰⁵ and R⁰⁰⁶, R⁰⁰⁵ and R⁰⁰⁷, or R⁰⁰⁶ and R⁰⁰⁷, taken together,may form a ring with the carbon atom to which they are attached, thering having 3 to 16 carbon atoms, especially 3 to 12 carbon atoms.

Illustrative examples of the groups of formula (AL10) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl and2-tetrahydrofuranyloxycarbonylmethyl as well as substituent groups ofthe following formulae (AL10)-1 to (AL10)-9.

In formulae (AL10)-1 to (AL10)-9, R⁰⁰⁸ is independently a straight,branched or cyclic alkyl group of 1 to 8 carbon atoms or an aryl oraralkyl group of 6 to 20 carbon atoms; R⁰⁰⁹ is hydrogen or a straight,branched or cyclic alkyl group of 1 to 20 carbon atoms; R⁰¹⁰ is an arylor aralkyl group of 6 to 20 carbon atoms; and “a” is an integer of 0 to10.

Illustrative examples of the acetal group of formula (AL11) includethose of the following formulae (AL11)-1 to (AL11)-35.

The polymer may be crosslinked within the molecule or between moleculeswith acid labile groups of formula (AL11a) or (AL11b).

Herein R⁰¹¹ and R⁰¹² each are hydrogen or a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, or R⁰¹¹ and R⁰¹², taken together,may form a ring, and R⁰¹¹ and R⁰¹² are straight or branched alkylenegroups of 1 to 8 carbon atoms when they form a ring. R⁰¹³ is a straight,branched or cyclic alkylene group of 1 to 10 carbon atoms. Each of b andd is 0 or an integer of 1 to 10, preferably 0 or an integer of 1 to 5,and c is an integer of 1 to 7. “A” is a (c+1)-valent aliphatic oralicyclic saturated hydrocarbon group, aromatic hydrocarbon group orheterocyclic group having 1 to 50 carbon atoms, which may be separatedby a heteroatom such as oxygen, sulfur or nitrogen or in which some ofthe hydrogen atoms attached to carbon atoms may be substituted withhydroxyl, carboxyl, carbonyl groups or fluorine atoms. “B” is —CO—O—,—NHCO—O— or —NHCONH—.

Preferably, “A” is selected from divalent to tetravalent, straight,branched or cyclic alkylene, alkyltriyl and alkyltetrayl groups of 1 to20 carbon atoms, and arylene groups of 6 to 30 carbon atoms, which maybe separated by a heteroatom such as oxygen, sulfur or nitrogen or inwhich some of the hydrogen atoms attached to carbon atoms may besubstituted with hydroxyl, carboxyl, acyl groups or halogen atoms. Thesubscript c is preferably an integer of 1 to 3.

The crosslinking acetal groups of formulae (AL11a) and (AL11b) areexemplified by the following formulae (AL11)-36 through (AL11)-43.

Illustrative examples of the tertiary alkyl of formula (AL12) includetert-butyl, triethylcarbyl, 1-ethylnorbornyl, 1-methylcyclohexyl,1-ethylcyclopentyl, 2-(2-methyl)adamantyl, 2-(2-ethyl)adamantyl, andtert-amyl groups as well as those of (AL12)-1 to (AL12)-18.

Herein R⁰¹⁴ is independently a straight, branched or cyclic alkyl groupof 1 to 8 carbon atoms, or an aryl or aralkyl group of 6 to 20 carbonatoms; R⁰¹⁵ and R⁰¹⁷ each are hydrogen or a straight, branched or cyclicalkyl group of 1 to 20 carbon atoms; and R⁰¹⁶ is an aryl or aralkylgroup of 6 to 20 carbon atoms.

With R⁰¹⁸ representative of a di- or more valent alkylene or arylenegroup included as shown in formulae (AL12)-19 and (AL12)-20, the polymermay be crosslinked within the molecule or between molecules. In formulae(AL12)-19 and (AL12)-20, R⁰¹⁴ is as defined above; R⁰¹⁸ is a straight,branched or cyclic alkylene group of 1 to 20 carbon atoms or arylenegroup which may contain a heteroatom such as oxygen, sulfur or nitrogen;and c is an integer of 1 to 3.

The groups represented by R⁰¹⁴, R⁰¹⁵, R⁰¹⁶ and R⁰¹⁷ may contain aheteroatom such as oxygen, nitrogen or sulfur, examples of which areillustrated by those of the following formulae (13)-1 to (13)-7.

Of the acid labile groups of formula (AL12), recurring units having anexo-form structure represented by the formula (AL12)-21 are preferred.

Herein, R⁰¹⁹ is a straight, branched or cyclic alkyl group of 1 to 8carbon atoms or a substituted or unsubstituted aryl group of 6 to 20carbon atom; R⁰²⁰ to R⁰²⁵, R⁰²⁸ and R⁰²⁹ are each independently hydrogenor a monovalent hydrocarbon group of 1 to 15 carbon atoms which maycontain a heteroatom; and R⁰²⁶ and R⁰²⁷ are hydrogen. Alternatively, apair of R⁰²⁰ and R⁰²¹, R⁰²² and R⁰²⁴, R⁰²² and R⁰²⁵, R⁰²³ and R⁰²⁵, R⁰²³and R⁰²⁹, R⁰²⁴ and R⁰²⁸, R⁰²⁶ and R⁰²⁷, or R⁰²⁷ and R⁰²⁸, takentogether, may form a ring, and in this case, each R is a divalenthydrocarbon group of 1 to 15 carbon atoms which may contain aheteroatom. Also, a pair of R⁰²⁰ and R⁰²⁹, R⁰²⁶ and R⁰²⁹, or R⁰²² andR⁰²⁴ which are attached to adjoining carbon atoms may bond togetherdirectly to form a double bond. The formula also represents anenantiomer

Suitable alkyl groups include methyl, ethyl, propyl, isopropyl, butyl,isobutyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl and octyl,with those groups having 1 to 12 carbon atoms being preferred. Thepreferred aryl group is phenyl. Suitable monovalent hydrocarbon groupswhich may contain a heteroatom include alkyl groups as exemplifiedabove, methoxymethyl, methoxyethyl and methoxypropyl groups, with thosehaving 1 to 6 carbon atoms being preferred. Suitable divalenthydrocarbon groups which may contain a heteroatom include the foregoingmonovalent hydrocarbon groups with one of the hydrogen atoms attached tocarbon atoms being eliminated. When a pair of R⁰²⁰ and R⁰²¹ form a ring,for example, the ring preferably has 3 to 10 carbon atoms, morepreferably 3 to 8 carbon atoms.

The monomers of formula (1c) are described in U.S. Pat. No. 6,448,420(JP-A 2000-327633), and illustrative, non-limiting examples thereof aregiven below.

The acid labile groups of formula (AL12) also include acid labile groupshaving furandiyl, tetrahydrofurandiyl or oxanorbornanediyl asrepresented by formula (AL12)-22. It is preferred that these acid labilegroups be included in the recurring units derived from the monomers offormula (1c).

Herein, R⁰³⁰ and R⁰³¹ are each independently a straight, branched orcyclic monovalent hydrocarbon group of 1 to 10 carbon atoms. R⁰³⁰ andR⁰³¹, taken together, may form an aliphatic hydrocarbon ring with thecarbon atom to which they are attached. R⁰³² is a divalent groupselected from furandiyl, tetrahydrofurandiyl and oxanorbornanediyl. R⁰³³is hydrogen or a straight, branched or cyclic monovalent hydrocarbongroup of 1 to 10 carbon atoms which may contain a heteroatom.

Suitable monovalent hydrocarbon groups include alkyl groups. Suitablealiphatic hydrocarbon rings include those of 3 to 12 carbon atoms, forexample, cyclopentyl, cyclohexyl, norbornyl and adamantyl groups.

Examples of the monomers from which recurring units substituted withacid labile groups having furandiyl, tetrahydrofurandiyl andoxanorbornanediyl are derived are given below. Note that Me is methyland Ac is acetyl.

While the polymer to be compounded in the resist composition of theinvention includes essentially recurring units of formulae (1a), (2a)and (1b), it may have copolymerized therein recurring units havingadhesive groups other than formulae (1a), (2a) and (1b). Specifically,recurring units derived from monomers (1d), listed below, may beincorporated.

Monomers (1d)

In the polymer of the invention, the units of formulae (1a), (2a) and(1b) are present in molar proportions a1, a2 and b1, respectively, whichsatisfy the following range:0≦a1/(a1+a2+b1)≦0.9,

-   -   preferably 0≦a1/(a1+a2+b1)≦0.8,        0≦a2/(a1+a2+b1)≦0.9,    -   preferably 0≦a2/(a1+a2+b1)≦0.8,        0<(a1+a2)/(a1+a2+b1)<0.9,    -   preferably 0.03≦(a1+a2)/(a1+a2+b1)≦0.8, and        0<b1/(a1+a2+b1)≦0.8,    -   preferably 0.1≦b1/(a1+a2+b1)≦0.7.        Where units derived from the monomer of formula (1c) and units        derived from the monomer (1d) are incorporated in molar        proportions 1c and 1d, respectively, these proportions are        preferably in the following range:        0≦1c/(a1+a2+b1+1c+1d)≦0.8,    -   especially 0.1≦1c/(a1+a2+b1+1c+1d)≦0.7, and        0≦1d/(a1+a2+b1+1c+1d)≦0.7,    -   especially 0.1≦1d/(a1+a2+b1+1c+1d)≦0.6.        It is understood that the relative proportions of recurring        units of formulae (1a), (2a) and (1b) are the same whether the        denominator is (a1+a2+b1) or (a1+a2+b1+1c+1d).

The polymer of the invention should preferably have a weight averagemolecular weight (Mw) in the range of 1,000 to 500,000, more preferably2,000 to 30,000 as measured by gel permeation chromatography (GPC) usingpolystyrene standards. With too low a Mw, the resist composition may beless heat resistant. With too high a Mw, the resist composition may losealkali solubility and give rise to a footing phenomenon after patternformation.

If a polymer has a wide molecular weight distribution or dispersity(Mw/Mn), which indicates the presence of lower and higher molecularweight polymer components, there is a possibility that foreign matter isleft on the pattern or the pattern profile is degraded. The influencesof molecular weight and dispersity become stronger as the pattern rulebecomes finer. Therefore, the multi-component copolymer shouldpreferably have a narrow dispersity (Mw/Mn) of 1.0 to 2.0, especially1.0 to 1.5, in order to provide a resist composition suitable formicropatterning to a small feature size.

The polymer of the invention may be synthesized by any desired method,for example, by dissolving unsaturated bond-containing monomerscorresponding to the respective units of formulae (1a), (2a) and (1b)and optional monomers of formula (1c) or the like in an organic solvent,adding a radical initiator thereto, and effecting heat polymerization.Examples of the organic solvent which can be used for polymerizationinclude toluene, benzene, tetrahydrofuran, diethyl ether and dioxane.Examples of the polymerization initiator used herein include2,2′-azobisisobutyronitrile (AIBN),2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide.Preferably the system is heated at 50 to 80° C. for polymerization totake place. The reaction time is about 2 to 100 hours, preferably about5 to 20 hours. The acid labile group that has been incorporated in themonomers may be kept as such, or the acid labile group may be onceremoved with an acid catalyst and thereafter blocked or partiallyblocked.

The polymer of the invention can be formulated as the base resin into aresist composition, and especially chemical amplified positive workingresist composition. It is understood that on use of the polymer as thebase resin, a blend of two or more polymers which differ incompositional ratio, molecular weight distribution or molecular weightis acceptable.

In addition to the polymer, the positive resist composition of theinvention may comprise an organic solvent, a compound capable ofgenerating an acid in response to high-energy radiation (photoacidgenerator), and optionally, a dissolution inhibitor, a basic compound, asurfactant and other additives.

Solvent

The organic solvent used herein may be any organic solvent in which thebase resin, photoacid generator, and other components are soluble.Illustrative, non-limiting, examples of the organic solvent includeketones such as cyclohexanone and methyl-2-n-amylketone; alcohols suchas 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol,and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethylether, ethylene glycol monomethyl ether, propylene glycol monoethylether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether,and diethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate, propylene glycol monoethyl ether acetate,ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone.

These solvents may be used alone or in combinations of two or morethereof. Of the above organic solvents, diethylene glycol dimethylether, 1-ethoxy-2-propanol and propylene glycol monomethyl etheracetate, and mixtures thereof are preferred because the photoacidgenerator is most soluble therein.

The organic solvent is preferably used in an amount of about 200 to1,000 parts by weight, more preferably about 400 to 800 parts by weightper 100 parts by weight of the base resin.

Photoacid Generator

The photoacid generator is a compound capable of generating an acid uponexposure to high-energy radiation and includes the following:

-   (i) onium salts of the formula (P1a-1), (P1a-2) or (P1b),-   (ii) diazomethane derivatives of the formula (P2),-   (iii) glyoxime derivatives of the formula (P3),-   (iv) bissulfone derivatives of the formula (P4),-   (v) sulfonic acid esters of N-hydroxyimide compounds of the formula    (P5),-   (vi) β-ketosulfonic acid derivatives,-   (vii) disulfone derivatives,-   (viii) nitrobenzylsulfonate derivatives, and-   (ix) sulfonate derivatives.

These photoacid generators are described in detail.

(i) Onium Salts of Formula (P1a-1), (P1a-2) or (P1b):

Herein, R^(101a), R^(101b), and R^(101c) independently representstraight, branched or cyclic alkyl, alkenyl, oxoalkyl or oxoalkenylgroups of 1 to 12 carbon atoms, aryl groups of 6 to 20 carbon atoms, oraralkyl or aryloxoalkyl groups of 7 to 12 carbon atoms, wherein some orall of the hydrogen atoms may be replaced by alkoxy or other groups.Also, R^(101b) and R^(101c), taken together, may form a ring. R^(101b)and R^(101c) each are an alkylene group of 1 to 6 carbon atoms when theyform a ring. K⁻ is a non-nucleophilic counter ion.

R^(101a), R^(101b), and R^(101c) may be the same or different and areillustrated below. Exemplary alkyl groups include methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl,cyclopentyl, cyclohexyl, cycloheptyl, cyclopropylmethyl,4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl.Exemplary alkenyl groups include vinyl, allyl, propenyl, butenyl,hexenyl, and cyclohexenyl. Exemplary oxoalkyl groups include2-oxocyclopentyl and 2-oxocyclohexyl as well as 2-oxopropyl,2-cyclopentyl-2-oxoethyl, 2-cyclohexyl-2-oxoethyl, and2-(4-methylcyclohexyl)-2-oxoethyl. Exemplary oxoalkenyl groups include2-oxo-4-cyclohexenyl and 2-oxo-4-propenyl. Exemplary aryl groups includephenyl and naphthyl; alkoxyphenyl groups such as p-methoxyphenyl,m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl; alkylnaphthyl groups such asmethylnaphthyl and ethylnaphthyl; alkoxynaphthyl groups such asmethoxynaphthyl and ethoxynaphthyl; dialkylnaphthyl groups such asdimethylnaphthyl and diethylnaphthyl; and dialkoxynaphthyl groups suchas dimethoxynaphthyl and diethoxynaphthyl. Exemplary aralkyl groupsinclude benzyl, phenylethyl, and phenethyl. Exemplary aryloxoalkylgroups are 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl,2-(1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl. Examples ofthe non-nucleophilic counter ion represented by K⁻ include halide ionssuch as chloride and bromide ions, fluoroalkylsulfonate ions such astriflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate,arylsulfonate ions such as tosylate, benzenesulfonate,4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, andalkylsulfonate ions such as mesylate and butanesulfonate.

Herein, R^(102a) and R^(102b) independently represent straight, branchedor cyclic alkyl groups of 1 to 8 carbon atoms. R¹⁰³ represents astraight, branched or cyclic alkylene group of 1 to 10 carbon atoms.R^(104a) and R^(104b) independently represent 2-oxoalkyl groups of 3 to7 carbon atoms. K⁻ is a non-nucleophilic counter ion.

Illustrative of the groups represented by R^(102a) and R^(102b) aremethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl,cyclopropylmethyl, 4-methylcyclohexyl, and cyclohexylmethyl.Illustrative of the groups represented by R¹⁰³ are methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene,1,4-cyclohexylene, 1,2-cyclohexylene, 1,3-cyclopentylene,1,4-cyclooctylene, and 1,4-cyclohexanedimethylene. Illustrative of thegroups represented by R^(104a) and R^(104b) are 2-oxopropyl,2-oxocyclopentyl, 2-oxocyclohexyl, and 2-oxocycloheptyl. Illustrativeexamples of the counter ion represented by K⁻ are the same asexemplified for formulae (P1a-1) and (P1a-2).

(ii) Diazomethane Derivatives of Formula (P2)

Herein, R¹⁰⁵ and R¹⁰⁶ independently represent straight, branched orcyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms, arylor halogenated aryl groups of 6 to 20 carbon atoms, or aralkyl groups of7 to 12 carbon atoms.

Of the groups represented by R¹⁰⁵ and R¹⁰⁶, exemplary alkyl groupsinclude methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl, octyl, amyl, cyclopentyl, cyclohexyl,cycloheptyl, norbornyl, and adamantyl. Exemplary halogenated alkylgroups include trifluoromethyl, 1,1,1-trifluoroethyl,1,1,1-trichloroethyl, and nonafluorobutyl. Exemplary aryl groups includephenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl,o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groupsinclude fluorophenyl, chlorophenyl, and 1,2,3,4,5-pentafluorophenyl.Exemplary aralkyl groups include benzyl and phenethyl.

(iii) Glyoxime Derivatives of Formula (P3)

Herein, R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ independently represent straight, branchedor cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms,aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkylgroups of 7 to 12 carbon atoms. Also, R¹⁰⁸ and R¹⁰⁹, taken together, mayform a ring. R¹⁰⁸ and R¹⁰⁹ each are a straight or branched alkylenegroup of 1 to 6 carbon atoms when they form a ring.

Illustrative examples of the alkyl, halogenated alkyl, aryl, halogenatedaryl, and aralkyl groups represented by R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ are thesame as exemplified for R¹⁰⁵ and R¹⁰⁶ Examples of the alkylene groupsrepresented by R¹⁰⁸ and R¹⁰⁹ include methylene, ethylene, propylene,butylene, and hexylene.

(iv) Bissulfone Derivatives of Formula (P4)

Herein, R^(101a) and R^(101b) are as defined above.

(v) Sulfonic Acid Esters of N-Hydroxyimide Compounds of Formula (P5)

Herein, R¹¹⁰ is an arylene group of 6 to 10 carbon atoms, alkylene groupof 1 to 6 carbon atoms, or alkenylene group of 2 to 6 carbon atomswherein some or all of the hydrogen atoms may be replaced by straight orbranched alkyl or alkoxy groups of 1 to 4 carbon atoms, nitro, acetyl,or phenyl groups. R¹¹¹ is a straight, branched or cyclic alkyl group of1 to 8 carbon atoms, alkenyl, alkoxyalkyl, phenyl or naphthyl groupwherein some or all of the hydrogen atoms may be replaced by alkyl oralkoxy groups of 1 to 4 carbon atoms, phenyl groups (which may havesubstituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms, nitro, oracetyl group), hetero-aromatic groups of 3 to 5 carbon atoms, orchlorine or fluorine atoms.

Of the groups represented by R¹¹⁰, exemplary arylene groups include1,2-phenylene and 1,8-naphthylene; exemplary alkylene groups includemethylene, ethylene, trimethylene, tetramethylene, phenylethylene, andnorbornane-2,3-diyl; and exemplary alkenylene groups include1,2-vinylene, 1-phenyl-1,2-vinylene, and 5-norbornene-2,3-diyl. Of thegroups represented by R¹¹¹, exemplary alkyl groups are as exemplifiedfor R^(101a) to R^(101c); exemplary alkenyl groups include vinyl,1-propenyl, allyl, 1-butenyl, 3-butenyl, isoprenyl, 1-pentenyl,3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl, 3-hexenyl, 5-hexenyl,1-heptenyl, 3-heptenyl, 6-heptenyl, and 7-octenyl; and exemplaryalkoxyalkyl groups include methoxymethyl, ethoxymethyl, propoxymethyl,butoxymethyl, pentyloxymethyl, hexyloxymethyl, heptyloxymethyl,methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl, pentyloxyethyl,hexyloxyethyl, methoxypropyl, ethoxypropyl, propoxypropyl, butoxypropyl,methoxybutyl, ethoxybutyl, propoxybutyl, methoxypentyl, ethoxypentyl,methoxyhexyl, and methoxyheptyl.

Of the substituents on these groups, the alkyl groups of 1 to 4 carbonatoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl andtert-butyl; and the alkoxy groups of 1 to 4 carbon atoms includemethoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, andtert-butoxy. The phenyl groups which may have substituted thereon analkyl or alkoxy of 1 to 4 carbon atoms, nitro, or acetyl group includephenyl, tolyl, p-tert-butoxyphenyl, p-acetylphenyl and p-nitrophenyl.The hetero-aromatic groups of 3 to 5 carbon atoms include pyridyl andfuryl.

Illustrative examples of the photoacid generator include:

onium salts such as

-   diphenyliodonium trifluoromethanesulfonate,-   (p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate,    diphenyliodonium p-toluenesulfonate,-   (p-tert-butoxyphenyl)phenyliodonium p-toluenesulfonate,    triphenylsulfonium trifluoromethanesulfonate,-   (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethane-sulfonate,-   bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethane-sulfonate,-   tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,    triphenylsulfonium p-toluenesulfonate,-   (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,-   bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate,-   tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,-   triphenylsulfonium nonafluorobutanesulfonate,-   triphenylsulfonium butanesulfonate,-   trimethylsulfonium trifluoromethanesulfonate,-   trimethylsulfonium p-toluenesulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium    trifluoromethane-sulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate,-   dimethylphenylsulfonium trifluoromethanesulfonate,-   dimethylphenylsulfonium p-toluenesulfonate,-   dicyclohexylphenylsulfonium trifluoromethanesulfonate,-   dicyclohexylphenylsulfonium p-toluenesulfonate,-   trinaphthylsulfonium trifluoromethanesulfonate,-   (2-norbornyl)methyl(2-oxocyclohexyl)sulfonium    trifluoro-methanesulfonate,-   ethylenebis[methyl(2-oxocyclopentyl)sulfonium    trifluoro-methanesulfonate], and-   1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;

diazomethane derivatives such as

-   bis(benzenesulfonyl)diazomethane,-   bis(p-toluenesulfonyl)diazomethane,-   bis(xylenesulfonyl)diazomethane,-   bis(cyclohexylsulfonyl)diazomethane,-   bis(cyclopentylsulfonyl)diazomethane,-   bis(n-butylsulfonyl)diazomethane,-   bis(isobutylsulfonyl)diazomethane,-   bis(sec-butylsulfonyl)diazomethane,-   bis(n-propylsulfonyl)diazomethane,-   bis(isopropylsulfonyl)diazomethane,-   bis(tert-butylsulfonyl)diazomethane,-   bis(n-amylsulfonyl)diazomethane,-   bis(isoamylsulfonyl)diazomethane,-   bis(sec-amylsulfonyl)diazomethane,-   bis(tert-amylsulfonyl)diazomethane,-   1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane,-   1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and-   1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane;

glyoxime derivatives such as

-   bis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,-   bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,-   bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,-   bis-O-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,-   bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,-   bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,-   bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,-   bis-O-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,-   bis-O-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,-   bis-O-(methanesulfonyl)-α-dimethylglyoxime,-   bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,-   bis-O-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime,-   bis-O-(tert-butanesulfonyl)-α-dimethylglyoxime,-   bis-O-(perfluorooctanesulfonyl)-α-dimethylglyoxime,-   bis-O-(cyclohexanesulfonyl)-α-dimethylglyoxime,-   bis-O-(benzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(xylenesulfonyl)-α-dimethylglyoxime, and-   bis-O-(camphorsulfonyl)-α-dimethylglyoxime;

bissulfone derivatives such as

-   bisnaphthylsulfonylmethane, bistrifluoromethylsulfonylmethane,    bismethylsulfonylmethane, bisethylsulfonylmethane,    bispropylsulfonylmethane, bisisopropylsulfonylmethane,    bis-p-toluenesulfonylmethane, and bisbenzenesulfonylmethane;

β-ketosulfone derivatives such as

-   2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and-   2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane;

disulfone derivatives such as diphenyl disulfone deratives anddicyclohexyl disulfone derivatives;

nitrobenzyl sulfonate derivatives such as

-   2,6-dinitrobenzyl p-toluenesulfonate and-   2,4-dinitrobenzyl p-toluenesulfonate;

sulfonic acid ester derivatives such as

-   1,2,3-tris(methanesulfonyloxy)benzene,-   1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and-   1,2,3-tris(p-toluenesulfonyloxy)benzene; and

sulfonic acid esters of N-hydroxyimides such as

-   N-hydroxysuccinimide methanesulfonate,-   N-hydroxysuccinimide trifluoromethanesulfonate,-   N-hydroxysuccinimide ethanesulfonate,-   N-hydroxysuccinimide 1-propanesulfonate,-   N-hydroxysuccinimide 2-propanesulfonate,-   N-hydroxysuccinimide 1-pentanesulfonate,-   N-hydroxysuccinimide 1-octanesulfonate,-   N-hydroxysuccinimide p-toluenesulfonate,-   N-hydroxysuccinimide p-methoxybenzenesulfonate,-   N-hydroxysuccinimide 2-chloroethanesulfonate,-   N-hydroxysuccinimide benzenesulfonate,-   N-hydroxysuccinimide 2,4,6-trimethylbenzenesulfonate,-   N-hydroxysuccinimide 1-naphthalenesulfonate,-   N-hydroxysuccinimide 2-naphthalenesulfonate,-   N-hydroxy-2-phenylsuccinimide methanesulfonate,-   N-hydroxymaleimide methanesulfonate,-   N-hydroxymaleimide ethanesulfonate,-   N-hydroxy-2-phenylmaleimide methanesulfonate,-   N-hydroxyglutarimide methanesulfonate,-   N-hydroxyglutarimide benzenesulfonate,-   N-hydroxyphthalimide methanesulfonate,-   N-hydroxyphthalimide benzenesulfonate,-   N-hydroxyphthalimide trifluoromethanesulfonate,-   N-hydroxyphthalimide p-toluenesulfonate,-   N-hydroxynaphthalimide methanesulfonate,-   N-hydroxynaphthalimide benzenesulfonate,-   N-hydroxy-5-norbornene-2,3-dicarboxyimide methanesulfonate,-   N-hydroxy-5-norbornene-2,3-dicarboxyimide    trifluoromethane-sulfonate, and-   N-hydroxy-5-norbornene-2,3-dicarboxyimide p-toluenesulfonate.

Preferred among these photoacid generators are onium salts such astriphenylsulfonium trifluoromethanesulfonate,

-   (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethane-sulfonate,-   tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,    triphenylsulfonium p-toluenesulfonate,-   (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,-   tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,    trinaphthylsulfonium trifluoromethanesulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium    trifluoromethane-sulfonate,-   (2-norbornyl)methyl(2-oxocylohexyl)sulfonium    trifluoro-methanesulfonate, and-   1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;

diazomethane derivatives such as

-   bis(benzenesulfonyl)diazomethane,-   bis(p-toluenesulfonyl)diazomethane,-   bis(cyclohexylsulfonyl)diazomethane,-   bis(n-butylsulfonyl)diazomethane,-   bis(isobutylsulfonyl)diazomethane,-   bis(sec-butylsulfonyl)diazomethane,-   bis(n-propylsulfonyl)diazomethane,-   bis(isopropylsulfonyl)diazomethane, and-   bis(tert-butylsulfonyl)diazomethane;

glyoxime derivatives such as

-   bis-O-(p-toluenesulfonyl)-α-dimethylglyoxime and-   bis-O-(n-butanesulfonyl)-α-dimethylglyoxime;-   bissulfone derivatives such as bisnaphthylsulfonylmethane;-   and sulfonic acid esters of N-hydroxyimide compounds such as-   N-hydroxysuccinimide methanesulfonate,-   N-hydroxysuccinimide trifluoromethanesulfonate,-   N-hydroxysuccinimide 1-propanesulfonate,-   N-hydroxysuccinimide 2-propanesulfonate,-   N-hydroxysuccinimide 1-pentanesulfonate,-   N-hydroxysuccinimide p-toluenesulfonate,-   N-hydroxynaphthalimide methanesulfonate, and-   N-hydroxynaphthalimide benzenesulfonate.

These photoacid generators may be used singly or in combinations of twoor more thereof. Onium salts are effective for improving rectangularity,while diazomethane derivatives and glyoxime derivatives are effectivefor reducing standing waves. The combination of an onium salt with adiazomethane or a glyoxime derivative allows for fine adjustment of theprofile.

The photoacid generator is preferably added in an amount of 0.1 to 50parts, and especially 0.5 to 40 parts by weight, per 100 parts by weightof the base resin. Less than 0.1 part of the photoacid generator maygenerate a less amount of acid upon exposure, sometimes leading to apoor sensitivity and resolution whereas more than 50 parts of thephotoacid generator may adversely affect the transmittance andresolution of resist.

Dissolution Regulator

To the resist composition, a dissolution regulator or inhibitor may beadded. The dissolution regulator is a compound having on the molecule atleast two phenolic hydroxyl groups, in which an average of from 0 to 100mol % of all the hydrogen atoms on the phenolic hydroxyl groups arereplaced with acid labile groups or a compound having on the molecule atleast one carboxyl group, in which an average of 50 to 100 mol % of allthe hydrogen atoms on the carboxyl groups are replaced with acid labilegroups, both the compounds having a weight average molecular weightwithin a range of 100 to 1,000, and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having at least one carboxyl group includethose of formulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl; R²⁰³ is hydrogen, a straight orbranched C₁-C₈ alkyl or alkenyl, or —(R²⁰⁷)_(h)—COOH; R²⁰⁴ is—(CH₂)_(i)— (where i=2 to 10), a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom; R²⁰⁵ is a C₁-C₁₀ alkylene, a C₆-C₁₀arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R²⁰⁶ ishydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or ahydroxyl-substituted phenyl or naphthyl; R²⁰⁷ is a straight or branchedC₁-C₁₀ alkylene; R²⁰⁸ is hydrogen or hydroxyl; the letter j is aninteger from 0 to 5; u and h are each 0 or 1; s, t, s′, t′, s″, and t″are each numbers which satisfy s+t=8, s′+t′=5, and s″+t″=4, and are suchthat each phenyl structure has at least one hydroxyl group; and α is anumber such that the compounds of formula (D8) or (D9) have a molecularweight of from 100 to 1,000.

The foregoing compounds should have a weight average molecular weight offrom 100 to 1,000, preferably 150 to 800. The dissolution inhibitor maybe formulated in an amount of 0 to 50 parts, preferably 5 to 50 parts,and more preferably 10 to 30 parts by weight, per 100 parts by weight ofthe base resin, and may be used singly or as a mixture of two or morethereof. An appropriate amount of the dissolution inhibitor is effectivefor improving resolution whereas more than 50 parts would lead toslimming of the patterned film, and thus a decline in resolution.

Basic Compound

The basic compound used herein is preferably a compound capable ofsuppressing the rate of diffusion when the acid generated by thephotoacid generator diffuses within the resist film. The inclusion ofthis type of basic compound holds down the rate of acid diffusion withinthe resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure, thus reducingsubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

Examples of suitable basic compounds include primary, secondary, andtertiary aliphatic amines, mixed amines, aromatic amines, heterocyclicamines, nitrogen-containing compounds having carboxyl group,nitrogen-containing compounds having sulfonyl group, nitrogen-containingcompounds having hydroxyl group, nitrogen-containing compounds havinghydroxyphenyl group, nitrogen-containing alcoholic compounds, amidederivatives, and imide derivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,iso-butylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine,di-iso-propylamine, di-n-butylamine, di-iso-butylamine,di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine,dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine,tri-iso-butylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic amines includeaniline derivatives (e.g., aniline, N-methylaniline, N-ethylaniline,N-propylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline,4-methylaniline, ethylaniline, propylaniline, trimethylaniline,2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline,2,6-dinitroaniline, 3,5-dinitroaniline, and N,N-dimethyltoluidine),diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine,phenylenediamine, naphthylamine, and diaminonaphthalene. Examples ofsuitable heterocyclic amines include pyrrole derivatives (e.g., pyrrole,2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole,and N-methylpyrrole), oxazole derivatives (e.g., oxazole andisooxazole), thiazole derivatives (e.g., thiazole and isothiazole),imidazole derivatives (e.g., imidazole, 4-methylimidazole, and4-methyl-2-phenylimidazole), pyrazole derivatives, furazan derivatives,pyrroline derivatives (e.g., pyrroline and 2-methyl-1-pyrroline),pyrrolidine derivatives (e.g., pyrrolidine, N-methylpyrrolidine,pyrrolidinone, and N-methylpyrrolidone), imidazoline derivatives,imidazolidine derivatives, pyridine derivatives (e.g., pyridine,methylpyridine, ethylpyridine, propylpyridine, butylpyridine,4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine,triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine,4-tert-butylpyridine, diphenylpyridine, benzylpyridine, methoxypyridine,butoxypyridine, dimethoxypyridine, 1-methyl-2-pyridine,4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl groupinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g., nicotinic acid, alanine, arginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable nitrogen-containing compounds having sulfonyl group include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, andnitrogen-containing alcoholic compounds include 2-hydroxypyridine,aminocresol, 2,4-quinolinediol, 3-indolemethanol hydrate,monoethanolamine, diethanolamine, triethanolamine,N-ethyldiethanolamine, N,N-diethylethanolamine, triisopropanolamine,2,2′-iminodiethanol, 2-aminoethanol, 3-amino-1-propanol,4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol,1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,3-piperidino- 1,2-propanediol, 3-pyrrolidino- 1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, andbenzamide. Suitable imide derivatives include phthalimide, succinimide,and maleimide.

One or more basic compounds of the following general formula (B)-1 mayalso be added.N(X)_(n)(Y)_(3-n)  (B)-1

In the formula, n is equal to 1, 2 or 3; side chain Y is independentlyhydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbonatoms which may contain an ether or hydroxyl group; and side chain X isindependently selected from groups of the following general formulas(X)-1 to (X)-3, and two or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched alkylene groups of 1 to 4 carbon atoms; R³⁰¹ and R³⁰⁴ areindependently hydrogen, straight, branched or cyclic alkyl groups of 1to 20 carbon atoms, which may contain at least one hydroxyl, ether,ester group or lactone ring; R³⁰³ is a single bond or a straight orbranched alkylene group of 1 to 4 carbon atoms; and R³⁰⁶ is a straight,branched or cyclic alkyl group of 1 to 20 carbon atoms, which maycontain at least one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the compounds of formula (B)-1 includetris(2-methoxymethoxyethyl)amine,

-   tris{2-(2-methoxyethoxy)ethyl}amine,-   tris{2-(2-methoxyethoxymethoxy)ethyl}amine,-   tris{2-(1-methoxyethoxy)ethyl}amine,-   tris{2-(1-ethoxyethoxy)ethyl}amine,-   tris{2-(1-ethoxypropoxy)ethyl}amine,-   tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,-   4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,-   4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,-   1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane,-   1-aza-12-crown-4,1-aza-15-crown-5,1-aza-18-crown-6,-   tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine,-   tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine,-   tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine,-   tris(2-pivaloyloxyethyl)amine,-   N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,-   tris(2-methoxycarbonyloxyethyl)amine,-   tris(2-tert-butoxycarbonyloxyethyl)amine,-   tris[2-(2-oxopropoxy)ethyl]amine,-   tris[2-(methoxycarbonylmethyl)oxyethyl]amine,-   tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,-   tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,-   tris(2-methoxycarbonylethyl)amine,-   tris(2-ethoxycarbonylethyl)amine,-   N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,-   N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,-   N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,-   N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,-   N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,-   N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,-   N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,-   N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,-   N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,-   N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,-   N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,-   N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,-   N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,-   N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,-   N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,-   N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,-   N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,-   N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)-ethylamine,-   N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)-ethylamine,-   N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,-   N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,-   N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,-   N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,-   N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,-   N-methyl-bis(2-acetoxyethyl)amine,-   N-ethyl-bis(2-acetoxyethyl)amine,-   N-methyl-bis(2-pivaloyloxyethyl)amine,-   N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,-   N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,-   tris(methoxycarbonylmethyl)amine,-   tris(ethoxycarbonylmethyl)amine,-   N-butyl-bis(methoxycarbonylmethyl)amine,-   N-hexyl-bis(methoxycarbonylmethyl)amine, and-   β-(diethylamino)-δ-valerolactone.

Also useful are basic compounds having cyclic structure, represented bythe following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branchedalkylene group of 2 to 20 carbon atoms which may contain one or morecarbonyl, ether, ester or sulfide groups.

Illustrative examples of the compounds having formula (B)-2 include1-[2-(methoxymethoxy)ethyl]pyrrolidine,

-   1-[2-(methoxymethoxy)ethyl]piperidine,-   4-[2-(methoxymethoxy)ethyl]morpholine,-   1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,-   1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,-   4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine,-   2-(1-pyrrolidinyl)ethyl acetate, 2-piperidinoethyl acetate,-   2-morpholinoethyl acetate, 2-(1-pyrrolidinyl)ethyl formate,-   2-piperidinoethyl propionate, 2-morpholinoethyl acetoxyacetate,-   2-(1-pyrrolidinyl)ethyl methoxyacetate,-   4-[2-(methoxycarbonyloxy)ethyl]morpholine,-   1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,-   4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine,-   methyl 3-(1-pyrrolidinyl)propionate,-   methyl 3-piperidinopropionate, methyl 3-morpholinopropionate,-   methyl 3-(thiomorpholino)propionate,-   methyl 2-methyl-3-(1-pyrrolidinyl)propionate,-   ethyl 3-morpholinopropionate,-   methoxycarbonylmethyl 3-piperidinopropionate,-   2-hydroxyethyl 3-(1-pyrrolidinyl)propionate,-   2-acetoxyethyl 3-morpholinopropionate,-   2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,-   tetrahydrofurfuryl 3-morpholinopropionate,-   glycidyl 3-piperidinopropionate,-   2-methoxyethyl 3-morpholinopropionate,-   2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate,-   butyl 3-morpholinopropionate,-   cyclohexyl 3-piperidinopropionate,-   α-(1-pyrrolidinyl)methyl-γ-butyrolactone,-   β-piperidino-γ-butyrolactone, β-morpholino-δ-valerolactone,-   methyl 1-pyrrolidinylacetate, methyl piperidinoacetate,-   methyl morpholinoacetate, methyl thiomorpholinoacetate,-   ethyl 1-pyrrolidinylacetate, and-   2-methoxyethyl morpholinoacetate.

Also, basic compounds having cyano group, represented by the followinggeneral formulae (B)-3 to (B)-6 are useful.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are eachindependently a straight or branched alkylene group of 1 to 4 carbonatoms.

Illustrative examples of the basic compounds having cyano group,represented by formulae (B)-3 to (B)-6, include

-   3-(diethylamino)propiononitrile,-   N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,-   N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,-   N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,-   N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,-   N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,-   methyl N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate,-   methyl N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate,-   methyl N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,-   N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,-   N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,-   N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,-   N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,-   N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,-   N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiono-nitrile,-   N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,-   N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,-   N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiono-nitrile,-   N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,-   N,N-bis(2-cyanoethyl)-3-aminopropiononitrile,    diethylaminoacetonitrile,-   N,N-bis(2-hydroxyethyl)aminoacetonitrile,-   N,N-bis(2-acetoxyethyl)aminoacetonitrile,-   N,N-bis(2-formyloxyethyl)aminoacetonitrile,-   N,N-bis(2-methoxyethyl)aminoacetonitrile,-   N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile,-   methyl N-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate,-   methyl N-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate,-   methyl N-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,-   N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,-   N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,-   N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,-   N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,-   N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,-   N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,-   N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,-   N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,-   N,N-bis(cyanomethyl)aminoacetonitrile,-   1-pyrrolidinepropiononitrile, 1-piperidinepropiononitrile,-   4-morpholinepropiononitrile, 1-pyrrolidineacetonitrile,-   1-piperidineacetonitrile, 4-morpholineacetonitrile,-   cyanomethyl 3-diethylaminopropionate,-   cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate,-   cyanomethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate,-   cyanomethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate,-   cyanomethyl N,N-bis(2-methoxyethyl)-3-aminopropionate,-   cyanomethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate,-   2-cyanoethyl 3-diethylaminopropionate,-   2-cyanoethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate,-   2-cyanoethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate,-   2-cyanoethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate,-   2-cyanoethyl N,N-bis(2-methoxyethyl)-3-aminopropionate,-   2-cyanoethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate,-   cyanomethyl 1-pyrrolidinepropionate,-   cyanomethyl 1-piperidinepropionate,-   cyanomethyl 4-morpholinepropionate,-   2-cyanoethyl 1-pyrrolidinepropionate,-   2-cyanoethyl 1-piperidinepropionate, and-   2-cyanoethyl 4-morpholinepropionate.

The basic compound is preferably formulated in an amount of 0.001 to 2parts, and especially 0.01 to 1 part by weight, per 100 parts by weightof the entire base resin. Less than 0.001 part of the basic compoundachieves no or little addition effect whereas more than 2 parts wouldresult in too low a sensitivity.

Other Components

In the positive resist composition, a compound having a group ≡C—COOHmay be blended. Exemplary, non-limiting compounds having a carboxylgroup include one or more compounds selected from Groups I and II below.Including this compound improves the PED stability of the resist andameliorates edge roughness on nitride film substrates.

Group I:

Compounds in which some or all of the hydrogen atoms on the phenolichydroxyl groups of the compounds of general formulas (A1) to (A10) belowhave been replaced with —R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight orbranched alkylene of 1 to 10 carbon atoms), and in which the molar ratioC/(C+D) of phenolic hydroxyl groups (C) to ≡C—COOH groups (D) in themolecule is from 0.1 to 1.0.

In these formulas, R⁴⁰⁸ is hydrogen or methyl; R⁴⁰² and R⁴⁰³ are eachhydrogen or a straight or branched C₁-C₈ alkyl or alkenyl; R⁴⁰⁴ ishydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or a—(R⁴⁰⁹)_(h)—COOR′ group (R′ being hydrogen or —R⁴⁰⁹—COOH); R⁴⁰⁵ is—(CH₂)_(i)— (wherein i is 2 to 10), a C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom; R⁴⁰⁶ is a C₁-C₁₀ alkylene, aC₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom;R⁴⁰⁷ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or ahydroxyl-substituted phenyl or naphthyl; R⁴⁰⁹ is a straight or branchedC₁-C₁₀ alkylene; R⁴¹⁰ is hydrogen, a straight or branched C₁-C₈ alkyl oralkenyl, or a —R⁴¹¹—COOH group; R⁴¹¹ is a straight or branched C₁-C₁₀alkylene; h is an integer of 1 to 4, j is an integer from 0 to 3; s1,t1, s2, t2, s3, t3, s4, and t4 are each numbers which satisfy s1+t1=8,s2+t2=5, s3+t3=4, and s4+t4=6, and are such that each phenyl structurehas at least one hydroxyl group; u is an integer of 1 to 4; κ is anumber such that the compound of formula (A6) may have a weight averagemolecular weight of 1,000 to 5,000; and λ is a number such that thecompound of formula (A7) may have a weight average molecular weight of1,000 to 10,000.

Group II:

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰², R⁴⁰³, and R⁴¹¹ are as defined above; R⁴¹² ishydrogen or hydroxyl; s5 and t5 are numbers which satisfy s5≧0, t5≧0,and s5+t5=5; and h′ is 0 or 1.

Illustrative, non-limiting examples of the compound having a carboxylgroup include compounds of the general formulas AI-1 to AI-14 and AII-1to AII-10 below.

In the above formulas, R″ is hydrogen or a —CH₂COOH group such that the—CH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, Kand X are as defined above.

The compound having a group ≡C—COOH may be used singly or ascombinations of two or more thereof. The compound is added in an amountranging from 0 to 5 parts, preferably 0.1 to 5 parts, more preferably0.1 to 3 parts, further preferably 0.1 to 2 parts by weight, per 100parts by weight of the base resin. More than 5 parts of the compound canreduce the resolution of the resist composition.

The positive resist composition of the invention may further include asurfactant which is commonly used for improving the coatingcharacteristics.

Illustrative, non-limiting, examples of the surfactant include nonionicsurfactants, for example, polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenolether and polyoxyethylene nonylphenol ether, polyoxyethylenepolyoxypropylene block copolymers, sorbitan fatty acid esters such assorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate,and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantrioleate, and polyoxyethylene sorbitan tristearate; fluorochemicalsurfactants such as EFTOP EF301, EF303 and EF352 (Tohkem Products Co.,Ltd.), Megaface F171, F172 and F173 (Dai-Nippon Ink & Chemicals, Inc.),Fluorad FC430 and FC431 (Sumitomo 3M Co., Ltd.), Asahiguard AG710,Surflon S-381, S-382, SC101, SC102, SC103, SC104, SC105, SC106, SurfynolE1004, KH-10, KH-20, KH-30 and KH-40 (Asahi Glass Co., Ltd.);organosiloxane polymers KP341, X-70-092 and X-70-093 (Shin-Etsu ChemicalCo., Ltd.), acrylic acid or methacrylic acid Polyflow No. 75 and No. 95(Kyoeisha Ushi Kagaku Kogyo Co., Ltd.). Inter alia, FC430, SurflonS-381, Surfynol E1004, KH-20 and KH-30 are preferred. These surfactantsmay be used alone or in admixture.

To the positive resist composition, the surfactant is added in an amountof up to 2 parts, preferably up to 1 part by weight, per 100 parts byweight of the base resin.

For the microfabrication of integrated circuits, any well-knownlithography may be used to form a resist pattern from the positiveresist composition of the invention although the technology is notlimited thereto.

The composition is applied onto a substrate (on which an integratedcircuit is to be formed, e.g., Si, SiO₂, SiN, SiON, TiN, WSi, BPSG, SOG,organic antireflective film, Cr, CrO, CrON, MoSi, etc.) by a suitablecoating technique such as spin coating, roll coating, flow coating, dipcoating, spray coating or doctor coating. The coating is prebaked on ahot plate at a temperature of 60 to 150° C. for about 1 to 10 minutes,preferably 80 to 120° C. for 1 to 5 minutes. The resulting resist filmis generally 0.1 to 2.0 μm thick. With a mask having a desired patternplaced above the resist film, the resist film is then exposed to actinicradiation such as UV, deep-UV, electron beams, x-rays, excimer laserlight, γ-rays and synchrotron radiation, preferably having an exposurewavelength of up to 300 nm, more preferably 180 to 200 nm. The exposuredose is preferably about 1 to 200 mJ/cm², more preferably about 10 to100 mJ/cm². The film is further baked on a hot plate at 60 to 150° C.for 1 to 5 minutes, preferably 80 to 120° C. for 1 to 3 minutes(post-exposure baking=PEB).

Thereafter the resist film is developed with a developer in the form ofan aqueous base solution, for example, 0.1 to 5 wt %, preferably 2 to 3wt % aqueous solution of tetramethylammonium hydroxide (TMAH) for 0.1 to3 minutes, preferably 0.5 to 2 minutes by conventional techniques suchas dip, puddle or spray techniques. In this way, a desired resistpattern is formed on the substrate. It is appreciated that the resistcomposition of the invention is suited for micro-patterning using suchhigh-energy radiation as deep UV with a wavelength of 254 to 193 nm,vacuum UV with a wavelength of 157 nm, electron beams, soft x-rays,x-rays, excimer laser light, γ-rays and synchrotron radiation, and bestsuitable for micro-patterning using high-energy radiation in thewavelength range of 180 to 200 nm.

Immersion lithography can be applied to the resist composition of theinvention. The ArF immersion lithography uses deionized water as theimmersion solvent. The immersion lithography involves prebaking a resistfilm and exposing the resist film to light through a projection lens,with water interposed between the resist film and the projection lens.Since water has a refractive index of 1.43 at the wavelength 193 nm, theexposure wavelength is 135 nm=193/1.43, indicating that the exposurewavelength can be shortened. Therefor, this technology is important forthe ArF lithography to survive to the 65 nm node, with a furtherdevelopment thereof being accelerated. The lactone ring, which is usedas a hydrophilic group in the prior art ArF resists, has solubility inboth alkaline aqueous solution and water. When lactones and acidanhydrides (e.g., maleic anhydride and itaconic anhydride) having highsolubility in water are used as the hydrophilic group, a problem arisesduring immersion in water that more water penetrates into the resistfrom its surface, whereby the resist surface is swollen. By contrast,hexafluoroalcohol is dissolvable in alkaline aqueous solution, but notat all in water, and it is thus believed that the influence ofdissolution and swelling during liquid immersion is minimized.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. The abbreviations used herein are AIBN for2,2′-azobisisobutyronitrile, GPC for gel permeation chromatography, NMRfor nuclear magnetic resonance, Mw for weight average molecular weight,Mn for number average molecular weight, Mw/Mn for molecular weightdistribution or dispersity, and PGMEA for propylene glycolmonomethylether acetate. For all polymers, Mw and Mn are determined byGPC versus polystyrene standards.

Synthesis Example 1

A 100-mL flask was charged with 8.2 g of3-ethyl-3-exo-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanyl methacrylate,9.2 g of 3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate,14.8 g of 2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)-cyclohexylmethacrylate, and 20 g of tetrahydrofuran as a solvent. The reactor wassubjected to cooling to −70° C. in a nitrogen atmosphere, evacuation tovacuum, and nitrogen flow, which procedure was repeated three times. Thereactor was warmed up to room temperature, charged with 0.2 g of AIBN asa polymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 25.8 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3-ethyl-3-exo-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanylmethacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-ylmethacrylate:2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate=0.30:0.40:0.30

Mw=8,200

Mw/Mn=1.78

This polymer is designated Inventive Polymer 1.

Synthesis Example 2

A 100-mL flask was charged with 9.8 g of 2-ethyl-2-adamantanemethacrylate, 8.2 g of 3-hydroxy-1-adamantyl methacrylate, 5.3 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]-nonan-9-yl methacrylate, 5.0 g of3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate, and 20 g of tetrahydrofuran as a solvent. The reactor wassubjected to cooling to −70° C. in a nitrogen atmosphere, evacuation tovacuum, and nitrogen flow, which procedure was repeated three times. Thereactor was warmed up to room temperature, charged with 0.2 g of AIBN asa polymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 23.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-ethyl-2-adamantane methacrylate:3-hydroxy-1-adamantylmethacrylate:3-oxo-2,7-dioxatricyclo-[4.2.1.0^(4,8)]nonan-9-ylmethacrylate:3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate=0.35:0.30:0.25:0.10

Mw=8,600

Mw/Mn=1.88

This polymer is designated Inventive Polymer 2.

Synthesis Example 3

A 100-mL flask was charged with 9.8 g of 2-ethyl-2-adamantanemethacrylate, 8.8 g of 3-hydroxy-1-adamantyl methacrylate, 10.2 g of3-oxo-5-methoxycarbonyl-2-oxatricyclo[4.2.1.0^(4,8)]-9-nonylmethacrylate, 5.0 g of3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate, and 20 g of tetrahydrofuran as a solvent. The reactor wassubjected to cooling to −70° C. in a nitrogen atmosphere, evacuation tovacuum, and nitrogen flow, which procedure was repeated three times. Thereactor was warmed up to room temperature, charged with 0.2 g of AIBN asa polymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 23.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-ethyl-2-adamantane methacrylate:3-hydroxy-1-adamantylmethacrylate:3-oxo-5-methoxycarbonyl-2-oxatricyclo[4.2.1.0^(4,8)]-9-nonylmethacrylate:3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate=0.35:0.30:0.25:0.10

Mw=8,900

Mw/Mn=1.83

This polymer is designated Inventive Polymer 3.

Synthesis Example 4

A 100-mL flask was charged with 9.8 g of 2-ethyl-2-adamantanemethacrylate, 8.2 g of 3-hydroxy-1-adamantyl methacrylate, 5.3 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]-nonan-9-yl methacrylate, 8.0 g of2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexyl methacrylate,and 20 g of tetrahydrofuran as a solvent. The reactor was subjected tocooling to −70° C. in a nitrogen atmosphere, evacuation to vacuum, andnitrogen flow, which procedure was repeated three times. The reactor waswarmed up to room temperature, charged with 0.2 g of AIBN as apolymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 23.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-ethyl-2-adamantane methacrylate:3-hydroxy-1-adamantylmethacrylate:3-oxo-2,7-dioxatricyclo-[4.2.1.0^(4,8)]nonan-9-ylmethacrylate:2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate=0.35:0.20:0.20:0.25

Mw=9,200

Mw/Mn=1.81

This polymer is designated Inventive Polymer 4.

Synthesis Example 5

A 100-mL flask was charged with 11.8 g of 1-cyclopentylcyclohexylmethacrylate, 8.2 g of 3-hydroxy-1-adamantyl methacrylate, 5.3 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.0 g of3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate, and 20 g of tetrahydrofuran as a solvent. The reactor wassubjected to cooling to −70° C. in a nitrogen atmosphere, evacuation tovacuum, and nitrogen flow, which procedure was repeated three times. Thereactor was warmed up to room temperature, charged with 0.2 g of AIBN asa polymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 23.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

1-cyclopentylcyclohexyl methacrylate:3-hydroxy-1-adamantylmethacrylate:3-oxo-2,7-dioxatricyclo-[4.2.1.0^(4,8)]nonan-9-ylmethacrylate:3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate=0.22:0.30:0.38:0.10

Mw=7,800

Mw/Mn=1.73

This polymer is designated Inventive Polymer 5.

Synthesis Example 6

A 100-mL flask was charged with 8.6 g of 1-ethylcyclopentylmethacrylate, 8.2 g of 3-hydroxy-1-adamantyl methacrylate, 5.3 g of3-oxo-2,7-dioxatricyclo-[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.0 g of3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate, and 20 g of tetrahydrofuran as a solvent. The reactor wassubjected to cooling to −70° C. in a nitrogen atmosphere, evacuation tovacuum, and nitrogen flow, which procedure was repeated three times. Thereactor was warmed up to room temperature, charged with 0.2 g of AIBN asa polymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 23.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

1-ethylcyclopentyl methacrylate:3-hydroxy-1-adamantylmethacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-ylmethacrylate:3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate=0.33:0.30:0.27:0.10

Mw=7,200

Mw/Mn=1.76

This polymer is designated Inventive Polymer 6.

Synthesis Example 7

A 100-mL flask was charged with 10.5 g of1-(7-oxanorbornan-2-yl)cyclopentyl methacrylate, 8.2 g of3-hydroxy-1-adamantyl methacrylate, 5.3 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.0 g of3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate, and 20 g of tetrahydrofuran as a solvent. The reactor wassubjected to cooling to −70° C. in a nitrogen atmosphere, evacuation tovacuum, and nitrogen flow, which procedure was repeated three times. Thereactor was warmed up to room temperature, charged with 0.2 g of AIBN asa polymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 23.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

1-(7-oxanorbornan-2-yl)cyclopentyl methacrylate 3-hydroxy-1-adamantylmethacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-ylmethacrylate:3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)-cyclohexylmethacrylate=0.25:0.30:0.35:0.10

Mw=7,800

Mw/Mn=1.88

This polymer is designated Inventive Polymer 7.

Synthesis Example 8

A 100-mL flask was charged with 7.9 g of 2-adamantyloxymethylmethacrylate, 8.2 g of 3-hydroxy-1-adamantyl methacrylate, 5.3 g of3-oxo-2,7-dioxa-tricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.0 g of3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate, and 20 g of tetrahydrofuran as a solvent. The reactor wassubjected to cooling to −70° C. in a nitrogen atmosphere, evacuation tovacuum, and nitrogen flow, which procedure was repeated three times. Thereactor was warmed up to room temperature, charged with 0.2 g of AIBN asa polymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 23.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-adamantyloxymethyl methacrylate:3-hydroxy-1-adamantylmethacrylate:3-oxo-2,7-dioxatricyclo-[4.2.1.0^(4,8)]nonan-9-ylmethacrylate:3,5-di(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate=0.21:0.30:0.41:0.08

Mw=9,100

Mw/Mn=1.83

This polymer is designated Inventive Polymer 8.

Comparative Synthesis Example 1

A 100-mL flask was charged with 24.4 g of 2-ethyl-2-adamantanemethacrylate, 17.1 g of γ-butyrolactone methacrylate, and 40 g oftetrahydrofuran as a solvent. The reactor was subjected to cooling to−70° C. in a nitrogen atmosphere, evacuation to vacuum, and nitrogenflow, which procedure was repeated three times. The reactor was warmedup to room temperature, charged with 0.2 g of AIBN as a polymerizationinitiator, heated at 60° C., and held for 15 hours for reaction. Thereaction solution was poured into 500 mL of isopropyl alcohol forprecipitation. The white solids were collected by filtration and driedat 60° C. under reduced pressure, yielding 36.1 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-ethyl-2-adamantane methacrylate:γ-butyrolactone methacrylate=0.48:0.52

Mw=12,500

Mw/Mn=1.88

This polymer is designated Comparative Polymer 1.

Comparative Synthesis Example 2

A 100-mL flask was charged with 8.7 g of2-(2-methoxymethoxy-1,1,1,3,3,3-hexafluoro-2-propyl)-cyclohexylmethacrylate, 25.7 g of2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexyl methacrylate,and 20 g of tetrahydrofuran as a solvent. The reactor was subjected tocooling to −70° C. in a nitrogen atmosphere, evacuation to vacuum, andnitrogen flow, which procedure was repeated three times. The reactor waswarmed up to room temperature, charged with 0.2 g of AIBN as apolymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 20.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-(2-methoxymethoxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate:2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate=0.77:0.23

Mw=6,700

Mw/Mn=1.56

This polymer is designated Comparative Polymer 2.

Comparative Synthesis Example 3

A 100-mL flask was charged with 8.6 g of 2-ethyl-2-adamantanemethacrylate, 30.3 g of2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexyl methacrylate,and 20 g of tetrahydrofuran as a solvent. The reactor was subjected tocooling to −70° C. in a nitrogen atmosphere, evacuation to vacuum, andnitrogen flow, which procedure was repeated three times. The reactor waswarmed up to room temperature, charged with 0.2 g of AIBN as apolymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 28.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-ethyl-2-adamantanemethacrylate:2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate 0.35:0.65

Mw=7,800

Mw/Mn=1.66

This polymer is designated Comparative Polymer 3.

Comparative Synthesis Example 4

A 100-mL flask was charged with 11.8 g of3,5-di(2-methoxymethoxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate, 35.6 g of2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexyl methacrylate,and 20 g of tetrahydrofuran as a solvent. The reactor was subjected tocooling to −70° C. in a nitrogen atmosphere, evacuation to vacuum, andnitrogen flow, which procedure was repeated three times. The reactor waswarmed up to room temperature, charged with 0.2 g of AIBN as apolymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 32.3 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3,5-di(2-methoxymethoxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate:2-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexylmethacrylate=0.20:0.80

Mw=6,800

Mw/Mn=1.55

This polymer is designated Comparative Polymer 4.

Examples and Comparative Examples Preparation of Positive ResistCompositions

Resist solutions were prepared by dissolving the polymer and othercomponents in a solvent in accordance with the formulation shown inTable 1 and passing through a filter with a pore size of 0.2 μm. Thecomponents in Table 1 are as follows.

Polymer:

-   -   Inventive Polymers 1 to 8 resulting from Synthesis Examples 1 to        8    -   Comparative Polymers 1 to 4 resulting from Comparative Synthesis        Examples 1 to 4        Photoacid generator:

PAG1 of the following structural formula

Basic compound:

triethanolamine, TMMEA, AAA, and AACN of the following structuralformulae

Dissolution inhibitor:

DRI1 of the following structural formula

Organic solvent:

PGMEA

Exposure/patterning

On silicon wafers having a film of AR-19 (Shipley) coated to a thicknessof 82 nm, the resist solutions were spin coated, then baked on a hotplate at 120° C. for 60 seconds to give resist films having a thicknessof 250 nm.

The resist films were exposed by means of an ArF excimer laser steppermodel NSR-S305B (Nikon Corp., NA 0.68, σ 0.85, ⅔ annular illumination).Immediately exposure, the resist films were baked (PEB) at 110° C. for60 seconds and then developed for 60 seconds with a 2.38% aqueoussolution of tetramethylammonium hydroxide, obtaining positive patterns.

The resist patterns were evaluated. The exposure dose (mJ/cm²) whichprovided a 1:1 resolution to a 0.12-μm line-and-space pattern was thesensitivity. The minimum line width (nm) of a L/S pattern which wasascertained separate at this dose was the resolution of a test resist.Using a measuring SEM model S-9220 (Hitachi Ltd.), the 0.12-μm L/Spattern was measured for line edge roughness. A cross section of theresist was observed under a SEM model S4200 (Hitachi Ltd.). The resultsare also shown in Table 1.

TABLE 1 Photoacid Basic Dissolution Line edge Polymer generator compoundinhibitor Solvent Sensitivity Resolution Pattern roughness (pbw) (pbw)(pbw) (pbw) (pbw) (mJ/cm²) (μm) profile (3σ, nm) Example 1 InventivePAG1 triethanolamine — PGMEA 32 0.11 rectangular 7.2 Polymer 1 (2.5)(0.25) (800) (100) Example 2 Inventive PAG1 triethanolamine — PGMEA 310.11 rectangular 6.1 Polymer 2 (2.5) (0.25) (800) (100) Example 3Inventive PAG1 triethanolamine — PGMEA 35 0.10 rectangular 7.8 Polymer 3(2.5) (0.25) (800) (100) Example 4 Inventive PAG1 triethanolamine —PGMEA 31 0.10 rectangular 7.6 Polymer 4 (2.5) (0.25) (800) (100) Example5 Inventive PAG1 triethanolamine — PGMEA 22 0.11 rectangular 7.9 Polymer5 (2.5) (0.25) (800) (100) Example 6 Inventive PAG1 triethanolamine —PGMEA 26 0.10 rectangular 7.2 Polymer 6 (2.5) (0.25) (800) (100) Example7 Inventive PAG1 triethanolamine — PGMEA 28 0.10 rectangular 6.9 Polymer7 (2.5) (0.25) (800) (100) Example 8 Inventive PAG1 triethanolamine —PGMEA 20 0.11 rectangular 6.8 Polymer 8 (2.5) (0.25) (800) (100) Example9 Inventive PAG1 TMMEA — PGMEA 36 0.10 rectangular 6.5 Polymer 2 (2.5)(0.4) (800) (100) Example 10 Inventive PAG1 AAA — PGMEA 36 0.10rectangular 6.8 Polymer 2 (2.5) (0.4) (800) (100) Example 11 InventivePAG1 AACN — PGMEA 36 0.10 rectangular 6.8 Polymer 2 (2.5) (0.4) (800)(100) Example 12 Inventive PAG1 triethanolamine DRI1 PGMEA 28 0.11rectangular 6.3 Polymer 2 (2.5) (0.25) (10) (800) (100) ComparativeComparative PAG1 triethanolamine — PGMEA 28 0.12 rectangular 10.5Example 1 Polymer 1 (2.5) (0.25) (800) (100) Comparative ComparativePAG1 triethanolamine — PGMEA — not — — Example 2 Polymer 2 (2.2) (0.25)(800) resolved (100) Comparative Comparative PAG1 triethanolamine —PGMEA 18 0.12 tapered 12.8 Example 3 Polymer 3 (2.2) (0.25) (800) (100)Comparative Comparative PAG1 triethanolamine — PGMEA 15 0.12 triangular11.5 Example 4 Polymer 4 (2.2) (0.25) (800) (100)

It is evident from Table 1 that the resist compositions of Examples 1 to12, when processed through ArF exposure, demonstrate a high sensitivity,an excellent resolution, and minimized line edge roughness.

Dissolution Behavior of Resist in Developer as Analyzed by QCM

The above-prepared resist solution (Example 1 or Comparative Example 1)was passed through a filter having a pore size of 0.2 μm, spin coated ona quartz substrate with a size of 1 inch (˜25 mm) having a goldundercoat and a chromium electrode vapor deposited thereon, and baked ona hot plate at 130° C. for 60 seconds, forming a resist film of 250 nmthick.

The resist film was exposed by means of an ArF exposure system ArFES3000(Litho Tech Japan Co., Ltd.) and baked (PEB) at 110° C. for 60 seconds.The substrate was set on a quartz oscillator microbalance instrumentRDA-Qz3 for resist development analysis (Litho Tech Japan Co., Ltd.).Development in a 2.38% aqueous solution of tetramethylammonium hydroxidewas carried out for 60 seconds, during which swell and dissolution weremeasured (oscillation mode AT cut). Exposure was made in a varyingexposure dose, and QCM measurement performed on every dose.

The results from the resist compositions of Example 1 and ComparativeExample 1 are plotted in FIGS. 1 and 2, respectively. In the chartsplotting resist film thickness versus developing time, an increase offilm thickness with developing time indicates swell, and a decrease offilm thickness with developing time indicates dissolution. It is seenthat the resist composition of Example 1 is significantly reduced inswell during development as measured by the QCM technique.

Dry Etching Test

Each polymer, 2 g, was thoroughly dissolved in 10 g of PGMEA, and passedthrough a filter having a pore size of 0.2 μm, obtaining a polymersolution. The polymer solution was spin coated onto a silicon substrateand baked, forming a polymer film of 300 nm thick. Dry etching testswere carried out on the polymer films by etching them under two sets ofconditions.

(1) CHF₃/CF₄ Gas Etching Test

Using a dry etching instrument TE-8500P (Tokyo Electron K.K.), thepolymer film was etched with CHF₃/CF₄ gas under the followingconditions. The difference in polymer film thickness before and afteretching was determined.

Chamber pressure 40.0 Pa RF power 1300 W Gap 9 mm CHF₃ gas flow rate 30ml/min CF₄ gas flow rate 30 ml/min Ar gas flow rate 100 ml/min Time 60sec(2) Cl₂/BCl₃ Gas Etching Test

Using a dry etching instrument L-507D-L (Nichiden Anerba K.K.), thepolymer film was etched with Cl₂/BCl₃ gas under the followingconditions. The difference in polymer film thickness before and afteretching was determined.

Chamber pressure 40.0 Pa RF power 300 W Gap 9 mm Cl₂ gas flow rate 30ml/min BCl₃ gas flow rate 30 ml/min CHF₃ gas flow rate 100 ml/min O₂ gasflow rate 2 ml/min Time 60 sec

The results of the etching tests are shown in Table 2.

TABLE 2 CHF₃/CF₄ gas etching Cl₂/BCl₃ gas etching Polymer rate (nm/min)rate (nm/min) Inventive Polymer 1 144 188 Inventive Polymer 2 138 186Inventive Polymer 3 126 168 Inventive Polymer 4 122 163 InventivePolymer 5 138 177 Inventive Polymer 6 150 203 Inventive Polymer 7 140180 Inventive Polymer 8 144 220 Comparative Polymer 1 158 350Comparative Polymer 2 225 338 Comparative Polymer 3 208 305 ComparativePolymer 4 285 408

As is evident from Tables 1 and 2, resist compositions using inventivepolymers not only exhibit an excellent sensitivity and resolution, andminimized line edge roughness when processed by ArF lithography, butalso have good dry etching resistance as demonstrated by a minimizeddifference in film thickness after etching.

Japanese Patent Application No. 2004-115088 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A resist composition comprising a polymer comprising recurring unitsof the general formulae (1a), (2a), and (1b):

wherein R¹ is each independently hydrogen or methyl, R² is eachindependently hydrogen, an acyl group of 1 to 10 carbon atoms, or anacid labile group, R³ is hydrogen, methyl or —CO₂R⁸, R⁴ is hydrogen,methyl or —CH₂CO₂R⁸, R⁵ to R⁷ are each independently hydrogen, methyl or—CO₂R⁹, R⁸ is each independently hydrogen or a straight, branched orcyclic alkyl group of 1 to 15 carbon atoms, R⁹ is hydrogen or astraight, branched or cyclic alkyl group of 1 to 10 carbon atoms, X is—CH₂—, —O— or —S—, with the proviso that X is not —CH₂— when all R⁵ toR⁷ are hydrogen, a1, a2 and b1 are numbers satisfying0≦a1/(a1+a2+b1)≦0.9,0≦a2/(a1+a2+b1)≦0.9,0<(a1+a2)/(a1+a2+b1)≦0.9, and0<b1/(a1+a2+b1)≦0.8.
 2. A chemically amplified positive resistcomposition comprising (A) the polymer of claim 1 as a base resin, (B)an organic solvent, and (C) a photoacid generator.
 3. The resistcomposition of claim 2, further comprising a dissolution inhibitor. 4.The resist composition of claim 2, further comprising a basic compoundand/or a surfactant.
 5. A process for forming a pattern comprising thesteps of applying the resist composition of claim 1 onto a substrate,heat treating, exposing to high-energy radiation, and developing with adeveloper.
 6. The pattern forming process of claim 5 wherein thehigh-energy radiation has a wavelength in the range of 180 to 200 nm.